This non-provisional application claims priority under 35 U.S.C. 119(a) on Korean Patent Application No. 2004-64641 filed on Aug. 17, 2004, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a composition for preparing a nanoporous material. More specifically, the present invention relates to a composition for preparing a material in which nanopores with a size of 20Å or less are uniformly distributed, the composition comprising i) a cyclodextrin derivative, ii) a thermostable matrix precursor, and iii) a solvent for dissolving the components i) and ii).
2. Description of the Related Art
Nanoporous materials have drawn attention as materials for adsorbents, supports for catalysts, thermal insulators and electrical insulators in various fields. With the increasing integration of semiconductor devices, the speed between wirings has a significant impact on the performance of the semiconductor devices. Accordingly, an interlayer dielectric film having a low storage capacity is required in order to lower the resistance and capacity between wirings. For this purpose, attempts have been made to use low dielectric constant materials for interlayer dielectric films. For instance, U.S. Pat. Nos. 3,615,272, 4,399,266 and 4,999,397 disclose polysilsesquioxanes having a dielectric constant of about 2.5˜3.1 prepared by spin-on deposition (“SOD”), which can replace SiO2 having a dielectric constant of around 4.00 prepared by a conventional chemical vapor deposition (CVD) technique. Further, U.S. Pat. No. 5,965,679 teaches polyphenylenes as organic polymers having a dielectric constant between about 2.65 and about 2.70. However, this dielectric constant range is not sufficiently low to satisfy an increasing demand to fabricate high-speed devices requiring an ultra-low dielectric constant of not higher than 2.50. For this reason, there have been a number of trials to incorporate air having a dielectric constant of 1.0 at the nanometer-scale level into an organic or inorganic material. A method is known for forming a nanoporous silica (SiO2) using tetraethoxysilane (“TEOS”) and an appropriate pore-forming agent by a sol-gel process. According to a method taught in U.S. Pat. No. 6,114,458, a lactone-based polymer in a dendrimeric form which can be decomposed at the thin film-forming stage is used as a porogen. A further method for preparing a material having a dielectric constant (K) lower than 3.0 is found in U.S. Pat. Nos. 6,107,357 and 6,093,636. According to this method, first, a particular amount of the lactone-based polymer or a vinyl-based polymer, e.g., polystyrene, polymethacrylate or polyester, in a dendrimeric form is mixed with an organic or inorganic matrix to form a thin film, and is then decomposed at high temperatures to form nano-scale pores.
However, the porous materials prepared by the aforementioned methods have problems that the pores have a size as large as 50 Å˜100 Å and are not uniformly distributed in the matrix.